All along CityPlace have gone with the masterplan exept maybe for Panarama which they squeezed between the Gardiner and Lakeshore,they have also co-operated with the city on building the future subsidized portion by Bathurst,they are going ahead with the park and the pedestrian bridge.i think they hold the cards on that Signature location and will build something tall and funky with not much feedback from the city.Remember this city land sat empty with no takers for 20 years waiting for development untill they came along.
The Master Plan is only one part of the process. They might have stuck to the number of planned buildings, location of buildings, transportation ROWs and various other aspects, but it all comes down to the individual Site Plan applications for each phase that determines the actual massing, density, etc. There are people within the City (planners and politicians, especially Adam Vaughan) who are not very happen with how CityPlace was planned on an overall basis, some of which was beyond their control (eg. lack of a design review panel). Concord does not hold all the cards. If they applied to get a rezoning for more density for Signature, I would expect resistance with 300 Front being a prime example of how the City didn't want a 58 (i think) storey building, and ended up being 51. Signature is even further west away from the 'core' than 300 Front with the whole tapered skyline debacle.
They are not building the affordable housing, TCHC is, who will probably issue a RFP to developers to build the market-value units on those blocks (beside Parade to the west). The park and the bridge are community benefits and are part of the section 37 concessions for the allowed increase in height and density.
And remember, the land sat vacant because of various issues such as large cost to purchase, potential environmental cleanup issues, and that same little recession thingy in the late 80s-early 90s. The City's original vision for that land was to be a second commercial/financial district, not a (basically) strictly residential area. The City dropped the ball by allowing this, and not sticking to some of the original plan and have more of a mixed-use area with some office and retail buildings (I don't mean separate big box buildings, but mixed)